A good Sparkle, Antec, or Enermax 350W or 400W should be fine. A lower speed XP might even be fine on a 300W, if it's a decent one...but it's really a good idea to get at least 350W. I have a pretty stocked 2200+ XP system (1600+ o/ced) and it runs like a champ with a 350W Antec.
🙂